[Translators] issues on strings for 3.10.1

[Thomas Bellmann]

It seems the countries for the geolocation_plugin.c sometimes were
named with their full name, e.g. "Lao People'S (sic!) Democratic
Republic" where the short name is Laos or "Iran, Islamic Republic Of"
for Iran, but 

The British Indian Ocean Territory consists as of today only of the
Chagos Archipelago.

| "Libyan Arab Jamahiriya" 
at Wikipedia gets redirected to "History of
Libya under Muammar Gaddafi"
My suggestion: Use just "Libya"

| "Svalbard and Jan Mayen"
~  is a statistical designation defined by ISO 3166-1 of two parts of
Norway under separate jurisdictions
http://en.wikipedia.org/wiki/Svalbard_And_Jan_Mayen

Typo at
| #: ../src/plugins/python/python_plugin.c:730
| […]
| "Gets executed whenever a compose window is opened, no matterif that
| opening happened"
                                                        ^^^^^^^^

Couldn't these two be merged?:
| #: ../src/prefs_matcher.c:384
| #, fuzzy
| msgid "headers values"
| msgstr "Werte in Kopfzeilen"

| #: ../src/prefs_matcher.c:1846
| #, fuzzy
| msgid "Headers values"
| msgstr "Werte in Kopfzeilen"

Here it is written "Claws-Mail" for once, on all other occurrences
"Claws Mail" is used:
| #: ../src/plugins/rssyl/rssyl_cb_menu.c:242
| msgid "Claws-Mail needs network access in order to update the feed."
| msgid_plural "Claws-Mail needs network access in order to update
| feeds."

In the Quicksearch information the variable S is mentioned as S in all
places except one – maybe this should be unified?
| #: ../src/gtk/quicksearch.c:461
| msgid "messages which contain S in the Sender field"
| msgstr "Nachrichten, die S in der 'Absender'-Kopfzeile enthalten"

| #: ../src/gtk/quicksearch.c:462
| msgid "true if execute \"S\" succeeds"
| msgstr "Wahr, wenn Ausführung von S erfolgreich"

The Perl plugin lacks translatable strings in the po file.